Recently, much attention has been given to graphene wires using graphene instead of metal wires. Graphene is a novel carbon material obtained by making graphite extremely thin. Like a carbon nano-tube, graphene has quantization conductivity (ballistic conductivity) and realizes quantization conductivity. Therefore, it is advantageous to use the same as a long-distance wire from the viewpoint of electrical conduction. Further, the graphene structure itself is an extremely thin film and can be formed by use of the CVD method. As a result, graphene has excellent matching with respect to a device wire formation process.
When graphene is used for an LSI wire structure, a multi-layered graphene structure obtained by laminating graphene layers in a multi-layered form is used. As a method for further reducing the resistance of the multi-layered graphene structure, it is effective to apply a technique for adding a different element into the graphene layer. For example, the mobility of carriers (electrons or holes) in a graphene sheet is raised by adding an element such as Br in between graphene layers and thus the resistance thereof can be reduced.
However, Br or the like that is an effective candidate as an additive element reacts with a metal material of W or Ti represented as a via material of an LSI wire and may etch and corrode the metal wire. Particularly, a significant problem occurs in a contact that lies on the upper-layer side of the graphene wire and is formed in direct contact with the multi-layered graphene wire.